Slab



FIG. 1 is a top plan view of a slab showing my new ornamental design; and,

FIG. 2 is a perspective view of the slab of FIG. 1 showing my new design on the top surface thereof. The broken lines in FIG. 2 of the slab are for illustrative proposes only and form no part of the claimed design. 

The ornamental design for a slab, as shown and described. 